CLEANING OF DAMAGED GEOTHERMAL WELLS BY HIGH PRESSURE FLUID INJECTION

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DEM - Demonstration contracts

Obiettivo

The project aim is to make reliable a new process which as given good results but with too high failure rate in dogger wells recovered when sulfides dammaged. A new jetting tool will be design and manufactured to eliminate jamming problems. Real scale experimentation would be carried out on a selected dogger doublet with monitoring of the break up and scales elimination. Conventional work over of geothermal wells uses mechanical action of rock bits, this new process being hydraulic causes less damage and allow at the end a more effective inhibitor treatment.Innovative method to clean dammaged geothermal wells.The new tools and procedures have been tested in full scale while cleaning the geothermal production well of Meaux Beauval 1 (GMX-5) from 17th to 22nd September 1990. This well is 2214 m deep with an average drift angle of 35 deg. No problems have been encountered and the inside calipers of the casing recorded after cleaning show that the efficiency of the new method is good and that all the scales have been removed.The granulometric distribution of the particules (by weight and size) obtained from representative samples taken while cleaning allowed to estimate the total solid volume removed from the well. This result can be compared to the result obtained by recording the inside diameter of the casing before and after the cleaning works.A new geometry has been designed for the jetting tool. The new design is closed to that of the stabilizers commonly used in the drilling strings with an helicoidal distribution of the nozzles. Two safety devices are placed above the tool and its indexation system : - a circulating sub just above the jetting tool - a disconnecting sub above the circulating subA new running procedure has been carried out. The casings are cleaned by sections of about 500 meters each which are completely cleaned oneafter the other.The following parameters are monitored or recorded :- total out-flow- turbidity- sulfides and iron concentration- granulometry of scaling- inside casing diameter before and after cleaning.